Plastic pellet sorting apparatus with extruded side-stream monitoring

An automated system is provided for selectively separating resin pellets having a gel count below a specified maximum from pellets having a gel count above the specified maximum, while the pellets are flowing in a pneumatic conveyor. The separation is based on an essentially continuous measurement in which a laser beam is utilized to detect the number of gels in a film made from pellets withdrawn as a sample stream from the main pellet stream. In response to the gel count measurement, a control signal is established that is utilized to manipulate a diverter valve located in the pneumatic conveyor, which diverts pastic pellet flow between a preferred storage means storing pellets having a low gel count and a secondary storage means for storing pellets having a higher gel count. In operation, a hold up tank is provided between the point from which the sample stream is withdrawn and the diverter valve, so that the plastic pellet flow can be delayed in the hold up tank for the amount of time required for the withdrawn sample stream to be converted into the film, whereby the gel count measurement is representative of the pellets passing through the diverter valve.